Mechanical Engineering

Engineering design is focussed on the development of artifacts and systems to satisfy specified functions. Current CAD systems provide little support integrating the modeling of the function, behavior, and form of designed artifacts throughout the design process. The support that is provided is primarily for decomposition of functions in the earliest of stages of design. These decomposed functions are then rarely used in later design stages, most likely because of lack of integration with traditional CAD systems. The focus of this paper is to investigate representations that may be used for maintaining the function and behavior structure through later stages of design and simulation. Four representations are evaluated for use in function representation for conceptual design, embodiment design, and design for manufacturing. These four representations include: Graph Grammars, Exemplars, Bond Graphs, and Function Converters. It is shown that different representations are more suited for different phases of design depending upon required design tasks and for representing different types of function knowledge. Finally, an approach to integration of these representations is proposed, synthesizing a hybrid representation based upon the strengths of the four identified strategies.

Feature technology has been evolving since the early 1980s, yet is still found in few commercial CAD systems. Traditional CAD systems provide support for geometric design and limited parametric design. Two basic approaches to feature modeling have been developed: design by features and feature recognition. Each of these methods provide specific tools to designers not provided in traditional CAD. A truly comprehensive system ought to integrate the advances in geometric modeling, parametric modeling, design by features, and feature recognition. A brief review of existing integrated systems is provided. Geometric representations, feature representations, and model integration schemes are discussed. Finally, a discussion of the issues involved with developing an integrated system is provided. These issues evolved from the development of such as system.

Developing objective measures for evaluating and measuring the complexity of design would facilitate (1) empirical studies that require the use of equivalent but different design problems, (2) the development of design curriculums, and (3) the comparison of computer aided design automation tools. This paper surveys and evaluates different approaches to defining complexity in design for the design problem, process, and product. Three fundamental aspects to complexity are identified, size, coupling, and solvability, and expanded with respect to the three elements of design, problem, process, and product. Alternative methods for measuring these characteristics of the design are based on computational, information, and traditional design views of complexity. A method of measuring size as it relates to complexity is proposed for measuring the information content of design. A second method is proposed for decomposing a graph-based representation of design that provides a measure of the interconnectedness as it relates to complexity. Finally, two methods are proposed for determining the solvability complexity of design based on the effort involved and the degree of freedom of design. These measures are developed specifically for parametric and geometric problems as found in the embodiment design, but these principles may be applied beyond this.

In this paper, two measures are proposed for valuation of size and coupling complexities of design products as abstracted by three distinct representations. The proposed size complexity measure is based on the information theoretic definition of complexity that connects the complexity of a design to the level of entropy, or uncertainty, inherent in the design product. The proposed coupling complexity measure evaluates the decomposability of the graph-based representation of design products. To validate the proposed measures, an experiment is conducted to calculate the complexities of three consumer products based on three product representations, namely, function structure, connectivity graph, and parametric associativity graph. The findings indicate that coupling and size are independent measures of a product’s complexity. Thus, it is recommended that both measures should be used. Further, the complexity of a product is not independent of the choice of representation model used to describe the product. This suggests that the complexity of a product will vary with the selected view. Finally, it is shown that the two approaches for measuring complexity of a product are generalizable and can be applied to different representations.

Recognized as essential to modern business, collaborative meetings are held to make decisions about product design, market definition, employee hiring, and many other factors that affect business operations. Based on the literature on group decision-making (a single collaboratively assigned selection from an array of choices), several hypothesis have been generated for further research based on three fundamental problems with group decision-making: impact of initial preference and time pressure, impact of group dynamics and politics, and the lack of an objective quantitative group preference. We suggest that group decision making should not be utilized unless there are objective criteria (i.e., money, time) that allow the group members to evaluate decision choices for determination of group preferences. Without these objective criteria, the use of group decision-making should be reserved for use in option generation (i.e. brainstorming), problem solving, or creative processes of an exploratory nature.

Modeling complex doctrinal behaviors to support military simulations has recently been extended to graphical interfaces, giving military subject matter experts the ability to create behaviors that can be automatically encoded. For example, the Composable Behavior Technology (CBT) system supports this modeling paradigm. We discuss how to extend CBT to capitalize on previously stored and validated behavior models, and how to apply casebased reasoning to this design problem. We propose an approach that incorporates text and graphical retrieval strategies and multiple levels of similarity analysis. Finally, we outline future research and development directions.

The procedure of developing a design method/tool appears to be intuitive and unsystematic as it varies across domains. To understand this procedure, a case study is conducted on an automotive reverse engineering design project which involved developing three design tools, of which one of them, 'Function-Component diagram', is studied in detail. The Function-Component diagram is a tool to represent components and their functions in a single graph allowing for comparison across different models and manufacturers of the artifact in consideration. We trace the development of this tool from the initial concept to the final form.

This paper discusses the roles that a graduate student coach experienced while working with an undergraduate design team in the development of a low, cost, low volume plastic injection modeling machine. Identified roles include: design tool teacher, design reviewer, project manager, and customer. A critique of the roles, including times spent in each role, is provided. This experience created generally higher satisfaction among the students and among the customers than had been previously seen in similar projects. Based upon this experience, it is justified to consider incorporating graduate design students as design coaches in senior design project teams.

This paper outlines a research instrument developed to analyze the relationship between communication modes, leadership styles, and team composition. The instrument is a survey that captures this information from collaborative design team members. This information can be correlated with team success, and the productive characteristics can be encouraged in future groups. The survey was distributed and analyzed in small numbers, and first round recommendations and student feedback are gathered. The developed instrument gathers background information on the student, group, and project. The project itself was defined in four stages: Problem Definition, Concept Generation, Concept Selection, and Concept Expansion. The students were asked questions about the team leadership style based on the Vroom-Yetton Model. The students were then asked how often they used various communication modes (verbal, textual, and graphical) when communicating Peer-to-Peer, Peer-to-Group, and Group as a Whole. These questions were repeated for each of the design stages. The instrument was structured and refined in order to analyze the behavior of undergraduate design students. It is intended to provide researchers and educators a tool to evaluate and critique collaborative behavior in order to streamline the design process. However, the survey was formulated broadly enough to be used in an industrial setting with small changes in the format to accommodate more experienced designers. The analysis of the original distribution revealed that the survey should be broken down into four parts corresponding to the four design stages and administered longitudinally. The authors of this paper attempt to find the specifics of the relationships between leadership styles, communication modes, and team structure in an undergraduate design environment. A deeper understanding of these relationships will assist team leaders at the academic and industrial level in creating more productive teams and maximizing the efficiency of communication.

Cellular structures having negative Poisson’s ratios can be designed to have high shear flexure properties. In this paper, the elastic limits of hexagonal honeycombs including the ones having negative Poisson’s ratios (NPR) are explored with various cell geometries under simple shear loading. While designing a shear modulus, e.g., G12∗ of 10 MPa, of hexagonal honeycombs, corresponding meso-structures are designed with three constituent materials; an aluminum alloy (7075-T6), a titanium alloy (Ti–6Al–4V), and a high strength steel (ANSI 4340). The in-plane linear elastic honeycomb model is employed to achieve the shear moduli of the hexagonal honeycombs made of the three constituent materials. The shear strengths, (τpl∗)12 and shear yield strains, (γpl∗)12 of hexagonal honeycombs are obtained from finite element analysis using ABAQUS. The titanium alloy honeycombs show a good shear flexure property having both high (τpl∗)12 and (γpl∗)12 when it is designed to the target G12∗. The re-entrant geometry makes honeycombs flexible associated with a high effective bending length.

This paper presents a method for evaluating the lightweightedness of a vehicle, specifically addressing those components whose primary purpose is to aid in manufacturing and assembly rather than to provide end-user function. Seven laziness indicators are described. These indicators are used to evaluate individual vehicle components to aid in identifying mass reduction potential and focus the attention of designers on components or assemblies with high potential for mass reduction. This method is applied to a complete automotive vehicle, demonstrating a mass savings potential of the overall vehicle of approximately 5% of the total mass of the vehicle. Jay participated in Clemson's cooperative education program where he completed three rotations for the Timken Company as a manufacturing engineer in a needle and thrust bearing manufacturing plant. As a graduate student, he interned for Techtronic Industries North America as a project engineer in the power tool division. For his master's thesis, his research focused on design methods.

This paper presents the energy absorption properties of hexagonal honeycomb structures of varying cellular geometries under high speed in-plane crushing. While the crushing responses in terms of energy absorption and densification strains have been extensively researched and reported, a gap is identified in the generalization of honeycombs with contr'olled and varying geometric parameters. This paper addresses this gap through a series of finite element (FE) simulations where the cell angle and the inclined wall thickness, are varied while maintaining a constant mass of the honeycomb structure. A randomly filled, nonrepeating design of experiments (DOEs) is generated to determine the effects of these geometric parameters on the output of energy absorbed and a statistical sensitivity analysis is used to determine the parameters significant for the crushing energy absorption of honeycombs. It is found that while an increase in the inclined wall thickness enhances the energy absorption of the structure, increases in either the cell angle or ratio of cell angle to inclined wall thickness have adverse effects on the output. Finally, the optimization results suggest that a cellular geometry with a positive cell angle and a high inclined wall thickness provides for maximum energy absorption, which is verified with a 6% error when compared to a FE simulation.

This paper presents the procedure and recommendations resulting from an original equipment manufacturer empirical study on an assembly time savings workshop. The focus of the workshop was to reduce the assembly time of an automotive vehicle by reverse engineering a vehicle currently in production and applying design for assembly guidelines. The workshop was conducted at the OEM's research and development laboratory in Germany and required a collaborative effort between the US manufacturing plant and the German design group. The organization, equipment needed, and method used to conduct the assembly workshop are discussed in detail. The outcomes of the empirical study include assembly time reductions as well as best practices for conducting a time savings workshop. Specific details about assembly time and time reduction are not included in this paper due to the proprietary nature of the project.